Scanning probe microscopy (SPM) is a technique that scientists use to analyze a sample material by monitoring interaction between a probe and the material. For example, atomic force microscopes (AFM) measure attractive and repulsive forces between a tip of a cantilevered probe and a material surface, both perpendicular or normal to the surface and parallel or lateral to the surface. Such forces can be displayed in image form as a function of the position of the tip as it scans across the surface of the material.
Raman spectroscopy is a technique where a light beam is directed onto a sample material surface to induce an inelastic conformational change of underlying atoms, causing the atoms to emit photons that are of the same energy of that lost (or gained) from the irradiated beam. The photons can be dispersed according to wavelength onto a CCD screen, forming the Raman spectrum, which is has characteristic peaks based on what type of atomic bonds are present in the sample. The spatial resolution of Raman spectroscopy is approximately equal to the focal spot size, which is approximately half of the wavelength.
Tip-enhanced Raman Spectroscopy (TERS) is a technique where light is focused into a junction between an SPM probe tip and a sample material, where a strong field enhancement amplifies a photon signal coming out of the junction. This results in greater spatial resolution as the limiting factor is the probe apex diameter rather than a confocal limit.